The present invention pertains in general to X-ray detectors and, more particularly, to a flat panel solid state X-ray detector for being disposed in an array.
The use of flat panel X-ray detectors has been known in the art as being capable of digitally x-ray imaging a human body under examination in real time. They are operable to convert incident X-rays directly into electric charges and obtain electric signals therefrom. Alternatively, there are provided indirect detectors which convert incident X-rays into light and then convert the light into electric charges, which electric charges are then converted into electric signals.
These flat panel X-ray detectors are useful in that they remove the need for film emulsions. There are two types of detectors, one which requires a relatively high voltage X-ray emission and one that requires a lower voltage X-ray emission. The higher voltage X-ray emissions are facilitated by detectors that utilize an amorphous selenium layer that is operable to collect electrons which are then stored in a capacitor. These capacitors can then be sampled in a sequential manner to extract a charge therefrom, which charge correlates to the amount of energy received from the X-rays, this being affected by the density of the material disposed between, the X-ray source and the surface of the detector. This type of detector is described in W. Zhao and J. A. Rowlands, xe2x80x9cA Large Area Solid-State Detector for Radiology Using Amorphous Selenium,xe2x80x9d SPIE Vol. 1651, Medical Imaging VI Instrumentation (1992) TP 134-143, which is incorporated herein by reference. The lower voltage X-ray detector utilizes a layer of hydrogenated amorphous silicon (a-Si:H) with a layer of heavy metal such as molybdenum (Mo) to form a Schottky diode. This Schottky diode is reverse biased and the charge collected on the anode thereof, which charge is then gated to a charge collection amplifier.
Flat panel x-ray detectors eliminate the requirement for processing and developing photographic film. The development process requires several minutes of time. Development of portable x-rays takes place at a central developing area distant from where the x-rays are performed. The most common film used in radiology is coated on both sides to increase x-ray beam absorption. This can potentially lead to unsharpness by a process of xe2x80x9cprint-throughxe2x80x9d. xe2x80x9cPrint-throughxe2x80x9d occurs when light is not absorbed by the film emulsion on one side and is transmitted through to the emulsion on the opposite side. The xe2x80x9cprint-throughxe2x80x9d image is unsharp on the film due to the increase in distance the non-absorbed light has to travel. With the current technique, the semiconductor sensor balls are offset in two to three layers trapping all light directed at the flat panel. The picture will then generate an almost instantaneous image upon a view screen. The entire imaging system currently in use is very dependent upon film processing. Steady state conditions must be maintained with regards to temperature conditions and concentration of developer and fixer. Any variance in the film development process can lead to poorer quality images and the risk of missed diagnoses.
Recently, radiologic images have been created on view screens using flat plate x-ray detectors. The clarity of the x-ray image is clinically judged by the resolution of the system. Resolution is defined as the capacity of the system to show details separated in the x-ray image if they are separated in the viewed object. The current system allows for increased sensitivity to improve resolution. Each ball sensor(s) relays evidence for energy detection to the central processing unit. The sensor on each ball encompasses only a small area and can send information signaling excitation only for that specific area.
The present invention disclosed and claimed herein comprises an X-ray detector. The X-ray detector includes a plurality of detector elements, each having a defined surface area and for detecting energy from impinging x-rays on the defined surface area to provide an output signal therefrom with a level corresponding to the energy of the impinging X-rays. A plurality of supporting substrates are provided, each for supporting at least one of the detector elements, each of the supporting substrates having a non-planar surface. A base is provided for supporting. the supporting substrates, such that the detector elements are directed in a substantially common direction. A processing system then processes the output of each of the detector elements to define a two-dimensional image.